It is generally known in the art to manufacture interior trim components for motor vehicles, such as door interior panels, trim inserts, dashboards, or consoles for example, from several individual layers of different materials. For example, it is typical to provide a thin-walled structural supporting layer as a substrate, a decorative cover material such as a decorative vinyl film, a synthetic leatherette layer, or a fabric, to cover the substrate, and a soft elastic material such as a synthetic polymer foam at least at one or more defined locations between the cover material and the substrate to provide a cushioned “soft touch” effect at this respective location.
It is also known to provide a foam layer or core between the cover material and the substrate, whereby this foam layer or core has a varying thickness at different locations of the trim component, for example including a substantially uniform foam layer thickness over most of the area of the trim component, and a greater thickness of the foam material at one or more areas that are intended to have an increased cushioning effect. Various different methods are known for manufacturing such foam cushioned trim components.
As a first example, it is known to pre-fabricate a form-stable structural supporting substrate of a synthetic plastic by means of an injection molding process, or of a wood fiber or natural fiber material by means of a press forming or molding process.
Thereby, the substrate is formed or molded to have the required three-dimensional contour shape. Next, one or more pre-cut foam insert members are glued with an adhesive onto appropriate defined locations on the pre-manufactured substrate, and then the entire unit including the substrate and the foam members fixed thereon is coated with an adhesive. Then, a decorative cover material layer is adhesively bonded and laminated onto the adhesive-coated substrate using a vacuum or pressing process.
It is a serious disadvantage that this known process requires four separate process steps or procedures. It is a further disadvantage that the required adhesives are not environmentally friendly and add an additional process step and complexity to the method. Perhaps most importantly, another significant aesthetic disadvantage is that the thick edges of the uniformly-thick foam insert members form rather sharp steps or transitions in the surface contour of the decorative cover material, so that the location and boundaries of the foam insert area are clearly visible due to this stepped transition of the surface of the cover material. In such a conventional method, it is not possible to achieve a smooth outer surface of the cover material, under which the foam cushioned areas are completely hidden.
A second conventional method also involves separate pre-fabrication of a formed or contoured structural substrate. The pre-fabricated substrate is then placed into an injection molding tool, and then a foaming polyurethane resin is injected into a cavity of the molding tool, so as to apply the foaming material directly onto the substrate. With an appropriate contouring of the molding tool, the thickness of the resulting foam material can be varied as desired, i.e. so that the foam material has the desired contour, and especially to avoid an abrupt step or transition in the thickness of the foam. After the foam has cured and solidified, the substrate and the foam thereon are coated with an adhesive, and then a decorative cover material is laminated thereon.
An advantage of this second known process is that the injected foam layer or pad can have the desired varying contour thickness so as to avoid a visually observable step or contour transition along the edges of the softer or more-cushioned area. It is a disadvantage, however, that this method requires at least four process steps or procedures. The materials used (e.g. polyurethane) are not very environmentally friendly. The foam injection equipment and molding tools increase the capital investment costs and the complexity of the method. Since the foam injection step followed by the curing and solidifying of the injected foam material requires substantially more time than the other steps of the method, it is typically necessary to provide plural injection molds or multi-position molding stations for each single manufacturing line, to avoid slowing down the overall production.